Photodynamic therapy (PDT) is the use of a medication activated by light. PDT for treating precancerous lesions (actinic keratoses) utilizes a topical (on the skin) solution in addition to a blue light. This treatment acts by selectively destroying precancerous cells, as well as shrinking sebaceous glands damaged by the sun.
The skin is swabbed to remove oils with acetone. Aminolevulinic acid is then applied to the skin and left on for a period of 60 minutes to 3 hours. The patient then rests in a reclining position with goggles on while a blue light shines on the skin for about 16 minutes Sunscreen is then applied following treatment.
A slight stinging, tingling or warm sensation may be noticeable during treatment with the blue light. We use a cooling fan to help decrease pain. Numbing cream is not helpful when using the blue light.
Redness, swelling, increased warmth and tingling sensations may occur for a few days following treatment. Redness and scaling may be present for up to 1 week, depending on the degree of sun damage. Rarely, crusting, darkening or lightening of areas of the skin, intense redness and prolonged swelling or stinging may occur. These generally resolve with proper skin care. Sun avoidance is absolutely necessary for 48 hours after the procedure. A sunscreen containing titanium and zinc oxide must be worn daily. Patients must wear a hat to protect the face from sunlight while outside during this 48 hour period as well.
PDT has been FDA approved for the treatment of precancerous lesions (actinic keratoses or AKs). The original FDA approval involved an overnight application of the Levulan medication, with light treatment the following day. Side effects and discomfort were much more unpleasant with this method. For this reason, PDT is more commonly being performed with 1-3 hour application time of Levulan. Many insurance companies require that a patient try prescription topical creams for their actinic keratoses before trying PDT.
Current recommendations suggest that 2 treatments are necessary to achieve results. In addition, precancerous lesions and sometimes very superficial skin cancers that are not yet visible on the skin can be cleared. Improvement likely lasts years with continued use of sunscreens, topical prescription medications for AKs and anti-aging creams such as retinoids (Retinol, Retin-A, Renova).